The present invention relates to sap flow, and more particularly relates to an integrated system for monitoring sap flow in a field and simultaneously performing data-logging and automatically scheduling irrigation therein.
As will be appreciated by those skilled in the art, water use is a crucial consideration worldwide, particularly in regions where water is scarce such as in arid climates and the like. Water consumption is, of course, of profound interest to practitioners engaged in viticulture. In view of the growing popularity of wines, it will be readily appreciated that the extent and frequency of irrigation and concomitant stress imposed upon grapes has been found to affect the quality thereof, and, ultimately, upon the quality of wine derived therefrom. There have been many approaches applied to deal with the phenomenon of stressed-plants.
What has previously been commonly regarded as evaporation transpiration, referred to as “ETP,” has now evolved into a panoply of phenomena including exposure to the sun, temperature, relative humidity, and wind speed, referred to as “ETO.” Using the crop water stress index (“CWSI”) has been found to be convenient for ascertaining the logistics associated with plant-stressing, wherein a zero CWSI value represents a well-watered, healthy plant. It will be understood that viticulturists generally control stress via deficit irrigation techniques. In the art, irrigation-scheduling has traditionally flowed from irrigation techniques based on timers, ETP-related modification of schedules, conducting soil moisture surveys, and, of course, time-tested heuristics. Such classical irrigation procedures have focused upon target markets that implicate commercial irrigation of crops, viticulture, orchards, oranges, apples, and stone fruit.
By continuously reporting the hourly water use rate of a tree, vine, or crop, a sap flow gage can record any change in the daily pattern of transpiration that reveals a shortage of water and the need for replenishing soil moisture supply. As an example, referring to FIG. 5, there is seen the sap flow of two trees, a peach and a pecan planted in lysimeters, compared with calculated demand. The trees were well-watered before the test, but sap flow was unable to keep up with demand. The peach tree sap flow declined 26% by the third day when faced with steady demand, thereby experiencing a water deficit. The water stress index may be easily calculated for plants having the same demand defined by the ETP, or by direct comparison of a well-watered plant (Tww) and a stressed plant (Tstr). The stress index for peach tree on the third day compared to the first day is therefore:CWSI=1−Tstr/Tww=1−60/81.3=0.26Using this convention, the tree with a stress index of zero has no transpiration drop; and the tree having a stress index of one is not transpiring. The crop stress index can be applied to any type of stress for heat, disease, pollution, or any other environmental factor. It should be evident to those skilled in the art that, when working with orchards or field crops, this information is invaluable since it is not directly obtainable in any other way.
As depicted in FIG. 6, Dynagages have a soft foam collar that surrounds its electronics. A Dynagage is installed on a stem having an axial length of at least the gage height, which is cleared of branches and smoothed. A weather shield is installed for outdoor applications and radiation shielding. O-rings are installed so as to allow enough room for an O-ring height above and the same distance below the gage. The specification for the gage diameter is the determining factor for selection of a gage, which fits properly. A worker in the field finds the diameter of the plants to be tested with a girth tape, or other measurement of the circumference. Then, this is converted into its diameter and the table of stem diameter ranges is checked. Choosing a gage that is the typical size or close to the minimum size has been found to provide ample room for plant growth. The sensor can also be moved higher on the stem to fit a smaller diameter, or moved lower to fit a larger diameter. An insulation wedge can be obtained to fill the gap when expanding the gage to its maximum diameter limit.
It will be appreciated that there are two data filters advised for general logger programs to check the quality of the underlying data, and to reject flow computations at periods when the sensor signals are either below the minimum threshold or above the maximum flow capacity of the sensor. The low flow rate filter takes care of the initial conditions where dT approaches zero, or less than zero, and it can also flag the user when a negative heat convection carried by the sap (“Qf”) is computed, in the instance of a thermal conductance constant for a particular installed sap flow gage (“Ksh”) setting not being made at its minimum value. Generally, the real-time filtering should be performed by the high capability loggers with the computational and logic capacity needed. With basic loggers, the logic and filtering should be performed afterwards. When the vertical and radial heat fluxes are subtracted from the power input, Qf is the remaining power carried by the sap. In the case of a zero flow rate on a very small stem, the temperature increases as dT approaches zero. For these cases the flow may be grossly exaggerated with a minor residual Qf. It will be understood that a true zero flow rate with accompanying dT of zero is rarely noticed on large plants, trees, or crop plants in a natural, growing condition. It will be appreciated that it takes only 3-4 grams per hour water flow to cause a positive dT on a 16 mm diameter plant.
Accordingly, these limitations and disadvantages of the prior art are overcome with the present invention, wherein a computer system is provided for monitoring sap flow in a field and simultaneously performing data-logging and automatically scheduling irrigation therein.